The present invention pertains to digital communication switching systems and more particularly to an enlarged capacity remotely located switching system which interconnects large central office systems to local subscribers or other smaller remotely located switching systems.
The networks of large modern day switching systems typically employ solid state digital time division switching techniques. An ever increasing number of telephone subscribers has provided for an increasing requirement for central office switching system capability. As population growth expands outward from large metropolitan areas, these growth areas require modern day telephone service. To meet this need and to provide for interfacing with the large digital switching systems, smaller remotely located digital switching systems are required.
In order for the smaller digital switching systems to operate efficiently, they must provide the capability of easily interfacing with their larger counterparts. These smaller switching systems provide for handling between a few hundred and a few thousand telephone subscribers. To provide effective, efficient and economical service to such a number of subscribers, a switching system must be tailored to serve a particular number of subscribers. Large time division switching systems may be able to fill the requirement of handling telephone subscriber traffic; however, they are inefficient and uneconomical because much of their capacity is unused.
One such switching system is a non-folded T-S-T modular network taught by U.S. Pat. No. 3,956,593, issued to A. A. Collins et al., on May 11, 1976.
Another large time-space-time switching network is taught in U.S. Pat No. 4,005,272, issued on Jan. 25, 1977, to A. A. Collins et al. Both of the above mentioned switching systems exhibit the problem that they would be uneconomical in applications of small remote unit switches as mentioned above.
Another large switching system is taught by U.S. Pat. Nos. 4,406,005; 4,399,369; 4,399,533; 4,399,534; 4,392,223; and 4,402,077, all issued to N. Simmons during 1983 and assigned to the same assignee as the present invention. These patents depict the switching network of the base unit of the GTD-5 EAX switching system. Again, use of these units would be uneconomical to provide service for up to a few thousand subscribers.
Accordingly, it is the object of the present invention to provide an effective, efficient and economical digital switching network for a remotely located switching system handling between a few hundred to a few thousand telephone subscribers.